Rotodynamic Pumps that Resist Clogging

ABSTRACT

The disclosure provides a rotodynamic pump that resists clogging when pumping fluid that contains solid particles having a density that is greater than the fluid. The pump also includes a rotatable impeller assembly having at least one of a front shroud or a rear shroud that separates the pumping cavity from and defines with a casing at least one respective front cavity or rear cavity. The pump casing also has a primary passage between the pumping cavity and the discharge collector cavity, and at least one auxiliary passage connecting the discharge collector cavity and the at least one front cavity or rear cavity, wherein rotation of the rotatable impeller assembly causes the solid particles to move from the at least one front cavity or rear cavity radially outward to and through the at least one auxiliary passage to the discharge collector cavity.

BACKGROUND

Field of the Invention

The present invention generally relates to rotodynamic pumps, which also are known as centrifugal pumps, and which in some configurations may be magnetically driven, and more particularly to rotodynamic pumps that resist clogging.

Description of the Related Art

Pumped fluids often contain solid particles or particulates having a density that is greater than the fluid. The solid particles can abrade bushings and cause clogging of a rotodynamic pump. The pumping cavities of prior art pumps normally are designed to be separated from a casing discharge collector cavity, presumably to maintain the best pump efficiency. A rotatable impeller may include a front and/or rear shroud that isolates a front cavity forward of or a rear cavity rearward of the vanes of the impeller, with such cavity being defined by the shroud and the pump casing. To obtain the smoothest flow and best pump efficiency, the outer ends of the vanes of the impeller typically are sized and arranged to be aligned with the inner end of a passage between the pumping cavity and a discharge collector cavity that surrounds the pumping cavity, and the passage generally is smaller in width than the discharge collector cavity. However, with such a configuration, solid particles within the fluid being pumped have a tendency to move past the front or rear shroud and accumulate in the front or rear cavity, eventually clogging the pump.

For rotodynamic pumps that utilize a magnetically driven rotatable impeller, it is common for the pump to additionally include a recirculation path that allows a small percentage of the pump fluid flow to recirculate from the discharge back to the suction side of the pump. This recirculation is used mostly for lubrication and cooling of bushings and for cooling of the canister, which may get hot due to electrical eddy currents generated by the magnetic coupling. The recirculation path also can become clogged by an accumulation of solid particles.

Some pumps have auxiliary vanes on an opposite side of the front or rear shroud, within the front or rear cavity. Such auxiliary vanes may assist in generating centrifugal force on the solid particles in the fluid within the front or rear cavity, which may prevent the solid particles from flowing into and through a recirculation path by flinging or forcing them outward within the front or rear cavity. Nevertheless, without the ability to evacuate the solid particles, rotodynamic pumps present a risk of clogging when pumping fluid that contains solid particles having a density that is greater than the fluid.

SUMMARY

The present disclosure provides a rotodynamic pump having a design that uses at least one relatively small auxiliary passage to allow the solid particles to exit the at least one front or rear cavity and to enter the discharge collector cavity, so that the solid particles may exit the pump. Advantageously, the at least one auxiliary passage has a minimal effect on pump efficiency, while effectively reducing the tendency of clogging the pump. The design also can be used in pumps that use dynamic seals between rotating parts or that are magnetically driven.

In a first aspect, the disclosure provides a rotodynamic pump for pumping fluid that resists clogging when pumping fluid that contains solid particles having a density that is greater than the fluid. The pump includes a stationary casing having a front portion, a rear portion, an inlet port, an outlet port, a pumping cavity, and a discharge collector cavity located radially outward from the pumping cavity and in fluid communication with the outlet. The pump also includes a rotatable impeller assembly having vanes that terminate along a side of at least one of a front shroud or a rear shroud, wherein the at least one of the front shroud or rear shroud separates the pumping cavity from and defines with the casing at least one respective front cavity or rear cavity. The stationary casing further includes a primary passage between the pumping cavity and the discharge collector cavity, and at least one auxiliary passage connecting the discharge collector cavity and the at least one front cavity or rear cavity, and wherein rotation of the rotatable impeller assembly imparts centrifugal force on solid particles within fluid in the at least one front cavity or rear cavity and causes the solid particles to move from the at least one front cavity or rear cavity radially outward to and through the at least one auxiliary passage to the discharge collector cavity.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and provided for purposes of explanation only, and are not restrictive of the subject matter claimed. Further features and objects of the present disclosure will become more fully apparent in the following description of the preferred embodiments and from the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In describing the preferred embodiments, reference is made to the accompanying drawing figures wherein like parts have like reference numerals, and wherein:

FIG. 1 provides a side view and a front view of an example rotodynamic pump connected to a motor using an adapter and shaft extension in a close-coupled fashion.

FIG. 2 provides a quarter-sectioned perspective view of the example pump of FIG. 1.

FIG. 3 provides an enlarged closer perspective view of the quarter-sectioned area of FIG. 2.

FIG. 4 provides a perspective view of the example pump of FIG. 1 with a sectioned front portion of the casing, showing radially extending auxiliary passages connected to a primary passage between a pumping cavity and a discharge collector cavity.

FIG. 5 provides a front view of the example pump of FIG. 1 with the sectioned front portion of the casing of FIG. 3.

FIG. 6 provides a perspective view of a sectioned front portion of a casing of a second example pump, showing auxiliary passages that are separate apertures between a pumping cavity and a discharge collector cavity.

FIG. 7 provides a side sectioned view of the casing of FIG. 6, showing the auxiliary passages that are separate apertures.

FIG. 8 provides a perspective view of a sectioned front portion of a casing of a third example pump, showing tangentially extending auxiliary passages connected to a primary passage between a pumping cavity and a discharge collector cavity.

FIG. 9 provides a front view of the third example pump of FIG. 8 with the sectioned front portion of the casing.

FIG. 10 provides an enlarged closer perspective view of a quarter-sectioned area of a fourth example pump.

FIG. 11 provides a front perspective view of the fourth example pump of FIG. 10 with a sectioned front portion of the casing, showing radially extending auxiliary passages connected to a primary passage between a rear cavity and a discharge collector cavity.

FIG. 12 provides a rear perspective view of the corresponding front sectioned portion of the fourth example pump of FIG. 10 showing radially extending auxiliary passages connected to a primary passage between a front cavity and a discharge collector cavity.

It should be understood that the drawings are not to scale. While some mechanical details of example rotodynamic pumps, including details of fastening means and other plan and section views of the particular components, have not been shown, such details are considered to be within the comprehension of those skilled in the art in light of the present disclosure. It also should be understood that the present disclosure and claims are not limited to the preferred embodiments illustrated.

DETAILED DESCRIPTION

Referring generally to FIGS. 1-12 and the written disclosure herein, it will be appreciated that rotodynamic pumps of the present disclosure generally may be embodied within numerous configurations, and it is contemplated and should be understood that such configurations include other rotodynamic pumps whether such pumps utilize dynamic seals between rotating parts or are magnetically driven.

Referring to a preferred first example embodiment, in FIGS. 1-5, an example rotodynamic pump 2 is shown connected to a motor adapter 4 that, in turn, is connected to a standard C-face electric motor 6. More particularly, a first flange 5 of the adapter 4 is connected to the motor 6 by use of a plurality of fasteners 8, such as threaded screws or other suitable means of connection. The pump 2 includes a casing 100, a discharge port 102 and an inlet port 104. In this example embodiment, the discharge port 102 is radially facing, while the inlet port 104 is axially facing, although alternative configurations may be utilized. The casing 100 includes a rear face 106 that is connected to a second flange 7 of the adapter 4 by use of a plurality of fasteners 10 that pass through apertures in the second flange 7 and engage threaded holes in the casing rear face 106. The casing 100 may be constructed of rigid materials, such as steel, stainless steel, cast iron or other metallic materials, or structural plastics or the like.

The first example pump 2 also includes a backplate 200 that has an outer flange 202. The backplate outer flange 202 is clamped between the casing 100 and the adapter 4 when connecting the pump 2 to the adapter 4 by installing the fasteners 10. Sealing is provided between the casing 100 and the backplate 200 by an O-ring 13, although other methods of sealing may be employed, such as use of a gasket, liquid sealant or the like.

The pump 2 also includes a rear cover 300 that has an outer flange 302. The rear cover 300 is connected to the backplate 200 by use of a plurality of fasteners, such as threaded screws that pass through apertures in the backplate 200 and engage threaded holes in a backplate rear face 208.

While the present disclosure is applicable to rotodynamic pumps more generally, the first example pump 2 also happens to be magnetically driven. As such, the pump 2 further includes a canister 400 that has an outer flange 402. The canister outer flange 402 is clamped between the backplate 200 and the rear cover 300 when connecting the rear cover 300 to the backplate 200. Sealing is provided between backplate 200 and the canister 400 by an O-ring 16, although other methods of sealing may be employed, such as use of a gasket, liquid sealant or the like. The canister 400 also includes a front portion 404 that includes a front face 406, within a front cavity 408 and an aperture 410 that passes through the front portion 404. The canister 400 may be constructed of rigid materials. It will be appreciated that common materials may be used, such as stainless steel, or low conductivity metals, such as alloy C-22 or alloy C-276, and it could be advantageous to use materials having very low electrical conductivity, such as silicon carbide, ceramic, polymers or the like.

Attached to the canister front portion 404 is a nose cap 500, which includes a threaded hole 502, and a rear extended portion 506 that fits into the canister front cavity 408. The nose cap 500 is attached to the canister 400 by a fastener 18, such as a threaded screw that passes through the aperture 410 in the front portion 404 and engages the threaded hole 502 in the rear of the nose cap 500. In this example embodiment, there is just one fastener 18, but it will be appreciated by one of skill in the art that a plurality of fasteners or other suitable fastening means may be employed. The shape of the canister front cavity 408 is not cylindrical, and it corresponds to a non-cylindrical shape of the nose cap extended portion 506, so as to prevent relative rotation between the nose cap 500 and canister 400 when connected by the fastener 18. It will be appreciated that other configurations or fastening methods may be used to prevent relative rotation of the nose cap 500. Sealing is provided between the canister 400 and the nose cap 500 by an O-ring 20, although other methods of sealing may be employed, such as use of a gasket, liquid sealant or the like.

The pump 2 further includes an inner magnet assembly 600 that includes an inner ring 640 which may be connected directly to a shaft, or in this example, to a shaft extension 620. The inner ring 640 has a central threaded aperture 642 and the shaft extension 620 has a mating externally threaded front portion 622, which is used to connect the inner ring 640 to the shaft extension 620. In this example embodiment, the shaft extension 620 and inner ring 640 are separate pieces, but it will be appreciated that they could be combined, so as to be a single piece, or a different method of connection may be used. The inner ring 640 may be constructed of rigid materials, but is preferably constructed of a material with high magnetic permeability, such as iron, carbon steel or the like.

The shaft extension 620 of this example includes an inner opening 624 that slidably receives a shaft 22 of the motor 6. The shaft extension 620 also includes a keyway 626 and one or more threaded apertures 628. A key 24 is positioned in the shaft extension keyway 626 and engages with a keyway 26 of the motor shaft 22, to provide a positive rotational connection between the shaft extension 620 and the motor shaft 22. One or more setscrews 28 are positioned in the shaft extension threaded apertures 628 and are tightened against the keyway 26 of the motor shaft 22, to provide a positive axial connection between the shaft extension 620 and the motor shaft 22.

The inner ring 640 includes an outer surface to which are connected twenty-four magnet segments 646, although it will be appreciated that one may have an embodiment with a different quantity of magnet segments. The magnet segments 646 are radially charged and are positioned with alternating polarity. The magnet segments 646 are rigidly connected to the inner ring 640 using an adhesive, although alternative suitable means of connection may be used, such as use of fasteners or the like. Although not required, this example embodiment includes an inner magnet sleeve 648 having a thin cylindrical portion that closely fits over and covers the outer surfaces of the magnet segments 646.

The first example pump 2 also includes a rotatable impeller assembly 700 that includes an impeller 702. The impeller 702 includes a rear opening 704, which receives an outer magnet assembly 705. The outer magnet assembly 705 includes an outer ring 706 having an inner surface to which are connected twenty-four magnet segments 710, which corresponds to the number of magnet segments connected to the inner ring 640, although it will be appreciated that one may have an embodiment with a greater or lesser quantity of magnet segments. The magnet segments 710 are radially charged and are positioned with alternating polarity. The magnet segments 710 are rigidly connected to the outer ring 706 using an adhesive, although alternative suitable means of connection may be used, such as use of fasteners or the like. An impeller magnet sleeve 712 is included having a thin cylindrical portion that closely fits along and covers the inner surfaces of the magnet segments 710. The impeller magnet sleeve 712 also includes a rear flange. The impeller magnet sleeve 712 is sealingly connected to the impeller 702 by continuous weld joints located at an outer end of the rear flange and at a front end of the cylindrical portion, although it will be appreciated by one of skill in the art that other methods of connection may be used, such as liquid adhesive, gaskets, O-rings or the like.

The impeller 702 has a central opening 724 that includes one or more grooves 726. A bushing 800 is received in the impeller central opening 724, and one or more O-rings are positioned between an outer surface of the bushing 800 and the grooves 726 in the central opening 724 of the impeller 702. The bushing outer surface is slightly smaller than the impeller central opening 724, and the O-rings are not intended to provide sealing between the two surfaces. Rather, in the event that the operating temperature may vary, and the bushing 800 and the impeller 702 may be made of materials with different rates of thermal expansion, then the size or extent of the clearance between the bushing 800 and impeller 702 will change and the compression of the O-rings of this example embodiment will accommodate this clearance change and will maintain a concentric relationship between the bushing 800 and the impeller 702. The rotor or impeller 702 may be constructed of rigid materials, such as steel, stainless steel, cast iron or other metallic materials, or structural plastics or the like. The outer ring 706 may be constructed of rigid materials, but preferably is constructed of a material with high magnetic permeability, such as iron, carbon steel or the like.

The impeller 702 further includes a rear surface 728 that includes one or more threaded holes 730. An impeller rear ring 732 is connected to the impeller rear surface 728 by at least one fastener 32, such as by a plurality of screws that pass through apertures in the impeller rear ring 732 and engage the threaded holes 730 in the impeller 702. The bushing 800 includes a rear portion with a shape that is not cylindrical, and it corresponds to a non-cylindrical central opening in the impeller rear ring 732 to prevent relative rotation between the bushing 800, the impeller rear ring 732 and the impeller 702. It will be appreciated that other configurations or fastening methods may be used to prevent relative rotation of the bushing 800.

The first example pump 2 also includes a stationary bearing sleeve 806 that has a cylindrical shape. The front portion 404 of the canister 400 includes an outer surface 412 having at least one groove 414. The bearing sleeve 806 is positioned over the outer surface 412 of the canister front portion 404, and at least one O-ring is positioned between the outer surface groove 414 of the canister front portion 404 and an inner surface of the bearing sleeve 806. In this example embodiment, two O-rings are received in two grooves 414. The outer surface 412 of the canister front portion 404 is slightly smaller than the inner surface of the bearing sleeve 806. In the event that the operating temperature may vary and the canister 400 and the bearing sleeve 806 may be made of materials with different rates of thermal expansion, then the size or extent of the clearance between the canister 400 and the bearing sleeve 806 will change. The O-rings are not intended to seal, but the compression of the O-rings in the grooves 414 will accommodate this clearance change and will maintain a concentric relationship between the canister 400 and the bearing sleeve 806.

The outer surface of the stationary bearing sleeve 806 is slightly smaller than the inner surface of the impeller bushing 800. The rotatable impeller assembly 700 rotates in engagement with and is supported by the outer surface of the stationary bearing sleeve 806.

The pump 2 of this example embodiment also includes a stationary rear thrust washer 814 having a central opening with a shape that is not cylindrical. The canister 400 includes a center portion having a non-cylindrical shape that corresponds to the shape of the central opening of the rear thrust washer 814, to prevent relative rotation between the canister 400 and rear thrust washer 814. It will be appreciated that other configurations or fastening methods may be used to prevent relative rotation of the thrust washer 814. The canister 400 includes a center wall 418 that has a front surface 420. The rear thrust washer 814 is brought into position over the canister front portion 416 and moved rearward against the front surface 420 of the canister center wall 418.

The pump 2 includes a stationary front thrust washer 818 with a central opening having a shape that is not cylindrical. The nose cap 500 includes a center portion having a non-cylindrical shape that corresponds to the shape of the central opening of the front thrust washer 818 to prevent relative rotation between the nose cap 500 and front thrust washer 818. It will be appreciated that other configurations or fastening methods may be used to prevent relative rotation of the front thrust washer 818. The nose cap 500 has a front flange 510. The front flange 510 also has a rear surface 512. The front thrust washer 818 is positioned over the center portion of the nose cap 500 and against the rear surface 512 of the front flange 510 of the nose cap 500.

The impeller bushing 800 has a length that is slightly shorter than the length of the bearing sleeve 806. The bearing sleeve 806 is positioned between the rear thrust washer 814 and the front thrust washer 818, creating a gap equal to the length of the bearing sleeve 806. The rotatable impeller assembly 700 is positioned such that the impeller bushing 800 is in the gap between the rear thrust washer 814 and the front thrust washer 818. The impeller bushing 800 has a front face and a rear face. Under some pump operating conditions, the rotatable impeller assembly 700 may experience a rear thrust force, pushing the rotatable impeller assembly 700 rearward and causing the bushing rear face to rotatably engage the front face of the rear thrust washer 814 and to restrict rearward motion of the rotatable impeller assembly 700. Under other pump operating conditions, the rotatable impeller assembly 700 may experience a forward thrust force, pushing the rotatable impeller assembly 700 forward and causing the bushing front face to rotatably engage the rear face of the front thrust washer 818 and to restrict forward motion of the rotatable impeller assembly 700. The bushing 800 may include one or more grooves on the front face, rear face and inner surface for lubrication.

The canister 400 includes a thin cylindrical portion 422 having an inner surface that is slightly larger than the outer surface of the inner magnet assembly 600, and having an outer surface that is slightly smaller than the inner surface of the impeller magnet sleeve 712. The casing 100, backplate 200, canister 400 and nose cap 500 all remain stationary, are sealingly connected, and together form a sealed chamber rearward of the canister 400.

The inner magnet segments 646 of the inner magnet assembly 600 are axially aligned with the impeller magnet segments 710 of the outer magnet assembly 705. The alternating polarity of the inner magnet segments 646 creates an inner magnetic field, and the alternating polarity of the impeller magnet segments 710 creates an outer magnetic field. These two magnetic fields synchronize together to provide a strong magnetic coupling torque between the inner magnet assembly 600 and the impeller assembly 700, such that when the motor 6 is energized, it rotates the motor shaft 22, which rotates the inner magnet assembly 600, which in turn, rotates the rotatable impeller assembly 700.

The impeller 702 of the rotatable impeller assembly 700 includes a plurality of vanes 740 that terminate along one side of a shroud 746, which in this example is the front side of a rear shroud. The front side of the shroud 746 has a surface 754 and in this example the shroud 746 is at the rear of the vanes 740. The casing 100 includes a discharge collector cavity 108 that is fluidly connected to the casing discharge port 102. The rotation of the impeller vanes 740 causes a pumping action in the location of the vanes 740, which is considered herein to be a pumping cavity 750, and moves fluid into the pump through the casing inlet port 104, radially outward through a primary passage 752 to the discharge collector cavity 108, and out of the pump through the discharge port 102.

In this first example pump 2, the shroud 746 separates the pumping cavity 750 from and defines with the casing 100 a rear cavity 110. The rear cavity 110 is partially blocked from the discharge collector cavity 108 by the impeller shroud 746. The casing 100 includes at least one auxiliary passage 112 that connects the discharge collector cavity 108 and the rear cavity 110. In this example, there are three auxiliary passages 112 spaced apart equally around the discharge collector cavity 108. In essence, while the primary passage 752 between the pumping cavity 750 and the collector discharge cavity 108 has a selected width, the auxiliary passage 112 expands the width of the primary passage 752 at the location of the auxiliary passage 112.

It will be appreciated that the rotatable impeller assembly could include a front shroud, a rear shroud, or both a front and rear shroud. Moreover, as is shown with the shroud 746, the at least one shroud has a surface 754 on the side along which the vanes 740 of the rotatable impeller assembly 700 terminate, and the surface 754 of the shroud 746 is substantially aligned with a surface 756 that defines the primary passage 752 between the pumping cavity 750 and the discharge collector cavity 108. For pumping efficiency, the primary passage 752 has a width at its inner end and the rotatable impeller assembly vanes 740 have outer ends sized to span a distance D that substantially aligns the outer end of the vanes 740 with the width at the inner end of the primary passage 752. It will be appreciated that the surfaces may be angled or other than directly radial, but will be aligned for a smooth transition from the shroud 746 and vanes 740 to the primary passage 752.

During pump operation, rotation of the rotatable impeller assembly 700 causes rotation of the fluid within the rear cavity 110, which imparts centrifugal force on any solid particles that may be within the fluid in the rear cavity 110, and causes the solid particles to move from the casing rear cavity 110 radially outward to and through the at least one auxiliary passage 112 to the discharge collector cavity 108. A casing having at least one such auxiliary passage 112 helps to resist clogging of the pump 2 by avoiding the accumulation of solid particles in the rear cavity 110 behind the shroud 746 of the rotatable impeller assembly 700. This allows the solid particles to escape to the discharge collector cavity 108, in this first example, through three auxiliary passages 112, while maintaining most or all of the efficiency advantage of a primary passage 752 being properly sized relative to the outer ends of the vanes 740 of the impeller 702. In the example shown, the rotatable impeller assembly 700 also may include at least one auxiliary vane located on the shroud 746 and within the rear cavity 110, which would further enhance the centrifugal force applied by the rotation of the rotatable impeller assembly 700 and assist in imparting centrifugal force on the solid particles within the fluid in the rear cavity 110.

While pump 2 is operating, the pumping action of the impeller vanes 740 creates a pressure differential within the pump 2, such that the pressure or suction within the inlet port 104 in front of the nose cap 500 is lower than the discharge pressure in the discharge collector cavity 108 and the outlet port 102. Fluid in the pump 2 moves radially inward within the rear cavity 110 due to the differential pressure in the fluid between suction at the pump inlet port 104 and discharge pressure at the pump outlet port 102. The movement of the fluid radially inward in the rear cavity 110 may help provide fluid for a recirculation passageway behind the rotatable impeller assembly 700 that begins at the discharge collector cavity 108, where the pressure is high, extends between stationary and rotating surfaces, and ends in front of the nose cap 500 at the inlet port 104, where the pressure is low. The passageway is dynamic, since every part is bounded by a combination of stationary surfaces and rotating surfaces. The stationary surfaces are on the casing 100, backplate 200, canister 400, rear thrust washer 814, bearing sleeve 806, front thrust washer 818 and nose cap 500. The rotating surfaces are on the rotatable impeller assembly 700.

Turning to FIGS. 6 and 7, a second example pump 2 a is shown. The second example pump 2 a is similar to the first example pump 2 in many ways and essentially uses the drive, sealing, rotatable impeller assembly, and other rear structures of the first example pump 2, but differs in that it includes an alternative pump casing 100 a, which is shown in a perspective sectioned view in FIG. 6 and in a side sectioned view in FIG. 7. Given the similarity between the majority of the components of the first and second example pumps, to avoid redundancy and unnecessary length, this description and the accompanying drawings, focus on the most relevant differences between the examples. For instance, instead of having at least one auxiliary passage 112 in the form of a groove, slot or channel that is open, connected to and effectively expands the width of a primary passage 752 at the location of the auxiliary passage 112, this alternative second example configuration includes at least one auxiliary passage 112 a in the form of a separate aperture. More particularly, the second example would have three auxiliary passages 112 a in the form of separate apertures that are spaced equally around the discharge collecting cavity 108 and that connect a rear cavity 110 to the collector discharge cavity 108.

The rotatable impeller assembly 700 still has an impeller 702 having a plurality of vanes 740. The vanes 740 terminate at a side of a shroud 746 that has a surface 754. For pumping efficiency, the primary passage 752 has a width at its inner end and the vanes 740 of the rotatable impeller assembly 700 have outer ends sized to span a distance D that substantially aligns the outer end of the vanes 740 with the width at the inner end of the primary passage 752. As with the first example, it will be appreciated that the surfaces may be angled or other than directly radial, but will be aligned for a smooth transition from the shroud 746 and vanes 740 to the primary passage 752. Accordingly, the surface 754 of the shroud 746 is substantially aligned with a surface 756 that defines the primary passage 752 between the pumping cavity and the discharge collector cavity 108. Thus, the main difference between the configuration and components of the second example pump 2 a relative to the first example pump 2 is the inclusion of at least one auxiliary passage in the form of an aperture 112 a, instead of at least one auxiliary passage in the form of a slot 112. However, the auxiliary passages 112 a in the form of apertures also would serve to resist pump clogging by allowing solid particles to pass from the rear cavity 110 to the collector discharge cavity 108.

Turning to FIGS. 8 and 9, a third example pump 2 b is shown. The third example pump 2 b is similar to the first example pump 2 in many ways and essentially uses the drive, sealing, rotatable impeller assembly, and other rear structures of the first example pump 2, but differs in that it includes an alternative pump casing 100 b, which is shown in a perspective sectioned view in FIG. 8 and in a front sectioned view in FIG. 9. Given the similarity between the majority of the components of the first and third example pumps, to avoid redundancy and unnecessary length, this description and the accompanying drawings, focus on the most relevant differences between the examples. For instance, instead of having at least one auxiliary passage 112 in the form of a groove, slot or channel that is open, extends radially outward, and is connected to and effectively expands the width of a primary passage 752 at the location of the auxiliary passage 112, this alternative third example configuration includes at least one auxiliary passage 112 b in the form of a similar groove, slot or channel, but extending tangentially outward, while being connected to and effectively expanding the width of the primary passage 752 at the location of the auxiliary passage 112 b. More particularly, the third example would have three auxiliary passages 112 b in the form of separate tangentially extending slots that are spaced equally around the discharge collecting cavity 108 and that connect a rear cavity 110 to the collector discharge cavity 108.

The rotatable impeller assembly 700 still has an impeller 702 having a plurality of vanes 740. The vanes 740 terminate at a side of a shroud 746 that has a surface 754. For pumping efficiency, the primary passage 752 has a width at its inner end and the vanes 740 of the rotatable impeller assembly 700 have outer ends sized to span a distance D that substantially aligns the outer end of the vanes 740 with the width at the inner end of the primary passage 752. As with the first example, it will be appreciated that the surfaces may be angled or other than directly radial, but will be aligned for a smooth transition from the shroud 746 and vanes 740 to the primary passage 752. Accordingly, the surface 754 of the shroud 746 is substantially aligned with a surface 756 that defines the primary passage 752 between the pumping cavity and the discharge collector cavity 108. Thus, the main difference between the configuration and components of the third example pump 2 b relative to the first example pump 2 is the inclusion of at least one auxiliary passage in the form of a slot 112 b that extends tangentially, instead of at least one auxiliary passage in the form of a slot 112 that extends more directly radially. However, the auxiliary passages 112 b extending tangentially also would serve to resist pump clogging by allowing solid particles to pass from the rear cavity 110 to the collector discharge cavity 108, and while radial and tangential angles have been shown, it will be appreciated that the auxiliary passages could extend outward at any angle.

Turning to FIGS. 10-12, a fourth example pump 2 c is shown, which is similar in many ways to the first example pump 2 and essentially uses the drive, sealing and other rear structures of the first example pump 2. Given the similarity between many of the components of the first and fourth example pumps, to avoid redundancy and unnecessary length, this description and the accompanying drawings, focus on the most relevant differences between the examples. For instance, the fourth example pump 2 c differs in that it includes an alternative casing 100 c and an alternative rotatable impeller assembly 700 c, having an alternative impeller 702 c, and having a rear shroud 746 and a front shroud 746 c, which are shown in an enlarged closer perspective view of a quarter-sectioned area of the fourth example pump in FIG. 10, in a front perspective view of a front sectioned portion in FIG. 11, and in a rear perspective view of the corresponding front sectioned portion of the fourth example pump 2 c.

The fourth example pump 2 c includes at least one auxiliary passage 112 that is similar to the at least one auxiliary passage 112 of the first example pump 2 in that it is in the form of a groove, slot or channel, and extends radially outward, while being connected to and effectively expanding the width of the primary passage 752 at the location of the auxiliary passage 112, so as to connect the rear cavity 110 with the discharge collector cavity 108. However, the fourth example pump 2 c also includes at least one auxiliary passage 112 c that is somewhat similar to the at least one auxiliary passage 112 in that it is in the form of a groove, slot or channel, and extends radially outward, but it is connected to and effectively expands the width of the primary passage 752 at the location of the auxiliary passage 112 c, so as to connect a front cavity 110 c that is forward of the shroud 746 c′ with the discharge collector cavity 108. More particularly, the fourth example pump 2 c would have three auxiliary passages 112 in the form of radially extending slots that are spaced equally around the discharge collecting cavity 108 and that connect a rear cavity 110 to the collector discharge cavity 108, while also having have three auxiliary passages 112 c in the form of radially extending slots that are spaced equally around the discharge collecting cavity 108 and that connect a front cavity 110 to the collector discharge cavity 108.

The alternative impeller 702 c of the rotatable impeller assembly 700 c of the fourth example pump 2 c includes a plurality of vanes 740 c having outer ends that extend between the rear shroud 746 and the front shroud 746 c. The outer ends of the vanes 740 c terminate at their rear at a front side of the rear shroud 746 that has a surface 754, and terminate at their front at a rear side of the front shroud 746 c that has a surface 754 c. The casing 100 c includes a discharge collector cavity 108 that is fluidly connected to the casing discharge port 102. The rotation of the impeller vanes 740 c causes a pumping action in the location of the vanes 740 c, which is considered herein to be a pumping cavity 750 c, and moves fluid into the pump through the casing inlet port 104, radially outward through a primary passage 752 to the discharge collector cavity 108, and out of the pump through the discharge port 102.

For pumping efficiency, the primary passage 752 has a width at its inner end and the vanes 740 c of the rotatable impeller assembly 700 c have outer ends sized to span a distance D that substantially aligns the outer end of the vanes 740 c with the width at the inner end of the primary passage 752. As with the first example, it will be appreciated that the surfaces may be angled or other than directly radial, but will be aligned for a smooth transition from the rear shroud 746 and front shroud 746 c and vanes 740 c to the primary passage 752. Accordingly, the surface 754 of the shroud 746 is substantially aligned with a surface 756 that defines one side of the primary passage 752 between the pumping cavity and the discharge collector cavity 108, with surface 754 c of the shroud 746 c similarly being substantially aligned with a surface 756 c that defines the other side of the primary passage 752. Thus, the main differences between the configuration and components of the fourth example pump 2 c relative to the first example pump 2 is the inclusion of at least a rear shroud 746 and a front shroud 746 c, which define with the casing 100 c a rear cavity 110 rearward of the rear shroud 746 and a front cavity 110 c forward of the front shroud 746 c, and the respective inclusion of at least one auxiliary passage 112 in the form of a slot that extends radially and connects the rear cavity 110 with the discharge collector cavity 108, as well as at least one auxiliary passage 112 c in the form of a slot that extends radially and connects the front cavity 110 c with the discharge collector cavity 108. The auxiliary passages 112 and 112 c extending radially also would serve to resist pump clogging by allowing solid particles to pass from the respective rear cavity 110 and front cavity 110 c to the collector discharge cavity 108.

From the above disclosure, it will be apparent that pumps constructed in accordance with this disclosure may include a number of structural aspects that provide advantages over conventional constructions, depending upon the specific design chosen.

It will be appreciated that a pump constructed in accordance with the present disclosure may be provided in various configurations. Any variety of suitable materials of construction, configurations, shapes and sizes for the components and methods of connecting the components may be utilized to meet the particular needs and requirements of an end user. Indeed, pumps in accordance with the present disclosure may include interior surfaces that are constructed of specific materials and/or have particular surface finishes wherein the interior surfaces permit use of the pumps in hygienic applications where microbial growth must be prevented. It will be apparent to those skilled in the art that various modifications can be made in the design and construction of such pumps without departing from the scope or spirit of the claimed subject matter, and that the claims are not limited to the preferred embodiment illustrated herein. It also will be appreciated that some aspects of the example embodiment are discussed in a simplified manner, as the invention is capable of being implemented in rotodynamic pumps, whether such pumps include dynamic seals between rotating parts or are magnetically driven. 

1. A rotodynamic pump that resists clogging when pumping fluid that contains solid particles having a density that is greater than the fluid, comprising: a stationary casing having a front portion, a rear portion, an inlet port, an outlet port, a pumping cavity, and a discharge collector cavity located radially outward from the pumping cavity and in fluid communication with the outlet; a rotatable impeller assembly comprising vanes that terminate along a side of at least one of a front shroud or a rear shroud, wherein the at least one of the front shroud or rear shroud separates the pumping cavity from and defines with the casing at least one respective front cavity or rear cavity; the stationary casing further comprising a primary passage between the pumping cavity and the discharge collector cavity, and at least one auxiliary passage connecting the discharge collector cavity and the at least one front cavity or rear cavity; and wherein rotation of the rotatable impeller assembly imparts centrifugal force on solid particles within fluid in the at least one front cavity or rear cavity and causes the solid particles to move from the at least one front cavity or rear cavity radially outward to and through the at least one auxiliary passage to the discharge collector cavity.
 2. The rotodynamic pump of claim 1, wherein the primary passage has a width and the rotatable impeller assembly vanes have outer ends sized to span a distance substantially similar to the width of the primary passage.
 3. The rotodynamic pump of claim 1, wherein the at least one front shroud or rear shroud has a surface on the side along which the vanes of the rotatable impeller assembly terminate, and wherein the surface is substantially aligned with a surface defining the primary passage between the pumping cavity and the discharge collector cavity.
 4. The rotodynamic pump of claim 1, wherein the rotatable impeller assembly further comprises at least one auxiliary vane located on the at least one front shroud or rear shroud and within the respective at least one front cavity or rear cavity; and wherein the at least one auxiliary vane located on the at least one front shroud or rear shroud assists in imparting centrifugal force on solid particles within the fluid.
 5. The rotodynamic pump of claim 1, wherein fluid moves radially inward within the at least one front cavity or rear cavity due to differential pressure in the fluid between suction at the pump inlet port and discharge pressure at the pump outlet port.
 6. The rotodynamic pump of claim 1, wherein the primary passage has a width and the at least one auxiliary passage is connected to and expands the width of the primary passage at the auxiliary passage.
 7. The rotodynamic pump of claim 1, wherein the auxiliary passage extends radially outward.
 8. The rotodynamic pump of claim 1, wherein the auxiliary passage extends tangentially outward.
 9. The rotodynamic pump of claim 1, wherein the at least one auxiliary passage is separate from the primary passage.
 10. The rotodynamic pump of claim 1, wherein the rotatable impeller assembly is magnetically driven. 